Mechanistic insights into the inhibitory effect of epigallocatechin gallate on the production of virulence factors in Proteus mirabilis.

This study aimed to elucidate the inhibitory effects of epigallocatechin gallate (EGCG) on virulence factors of Proteus mirabilis, a primary agent in catheter-associated urinary tract infections. The antimicrobial efficacy of EGCG was evaluated using the microdilution method, and the presence of biofilms and crystal formation were visualized using Gram staining and microscopy. Biochemical assays were performed to assess the inhibitory effects of EGCG on urease and hemolysin production. Swarming motility, a key determinant of bacterial colonization and spread, was evaluated using specialized swarming assays. Furthermore, the modulation of virulence-related gene expression by EGCG was quantitatively analyzed using quantitative real-time PCR, providing insights into its molecular mechanisms of action. EGCG exhibited a minimum inhibitory concentration of 94 μg/mL against P mirabilis, with a minimum bactericidal concentration of 188 μg/mL. EGCG significantly inhibited bacterial growth and hindered biofilm formation, and its inhibitory effect was positively correlated with EGCG concentration. EGCG markedly suppressed urease, hemolysin, and swarming motility, leading to notable reduction in crystal production. Furthermore, EGCG significantly downregulated the expression of virulence genes including flhB, flhD, speA, luxS, ureR, hpmA, and hpmB. EGCG demonstrated multifaceted inhibitory effects against P mirabilis, including growth, biofilm formation, crucial enzyme production, swarming motility, and inhibition of key virulence genes. These findings establish a robust experimental foundation for utilizing EGCG to treat infections induced by P mirabilis.